U.S. patent number 4,678,998 [Application Number 06/806,772] was granted by the patent office on 1987-07-07 for battery condition monitor and monitoring method.
This patent grant is currently assigned to Nissan Motor Company, Limited. Invention is credited to Kunihiro Muramatsu.
United States Patent |
4,678,998 |
Muramatsu |
July 7, 1987 |
Battery condition monitor and monitoring method
Abstract
A battery condition monitor and monitoring method uses known
relationships between battery impedance, remaining capacity and
remaining service life at different frequencies to detect remaining
capacity and remaining service life. The monitor includes a
computer for computing internal impedances of the storage battery
from different frequency components of voltage and amperage signals
from the battery, a memory for storing predetermined relationships
between the internal impedance, remaining capacity and remaining
service life of the storage battery for each of the frequencies and
a device for determining the remaining capacity and remaining
service life values for the storage battery in agreement at both or
all frequency values derives from the computed internal impedances.
The exact remaining capacity and service life of the storage
battery are continuously monitored.
Inventors: |
Muramatsu; Kunihiro (Yokosuka,
JP) |
Assignee: |
Nissan Motor Company, Limited
(JP)
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Family
ID: |
11790348 |
Appl.
No.: |
06/806,772 |
Filed: |
December 9, 1985 |
Foreign Application Priority Data
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Jan 25, 1985 [JP] |
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60-11891 |
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Current U.S.
Class: |
324/427;
340/636.11; 324/430; 340/636.15; 320/136 |
Current CPC
Class: |
G01R
31/3648 (20130101); G01R 31/389 (20190101); G01R
31/006 (20130101); G01R 31/386 (20190101); G01R
31/3842 (20190101) |
Current International
Class: |
G01R
31/36 (20060101); G01R 31/00 (20060101); G01N
027/46 () |
Field of
Search: |
;320/48 ;340/636
;324/57SS,426-431 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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53-127646 |
|
Aug 1978 |
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JP |
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2126735 |
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Mar 1984 |
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GB |
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Other References
Willihnganz: "Battery Impedance"-Electrical Engineering Sep.
1959-pp. 922-925..
|
Primary Examiner: Eisenzopf; Reinhard J.
Assistant Examiner: Solis; Jose M.
Attorney, Agent or Firm: Lowe, Price, LeBlanc, Becker &
Shur
Claims
What is claimed is:
1. A battery condition monitor for a storage battery into and out
of which currents flow, said currents having components of
different frequencies, comprising:
means for detecting a terminal voltage of the storage battery;
first means for extracting voltage frequency components from the
detected terminal voltage;
means for detecting an amperage of the currents;
second means for extracting amperage frequency components at the
same frequencies as said voltage frequency components from the
detected amperage;
means for computing internal impedances of the storage battery at
each of said frequencies from the voltage and amperage frequency
components;
means for storing predetermined relationships between the internal
impedance, remaining capacity and remaining service life of the
storage battery for each of said frequencies; and
means for determining the remaining capacity and remaining service
life values of the storage battery at said frequencies from the
computed internal impedances and said predetermined
relationships.
2. A battery condition monitor for a storage battery in an
automotive vehicle connected to an alternator, the storage battery
receiving and supplying currents having components of different
frequencies, comprising:
means for detecting a terminal voltage of the storage battery;
first means for extracting voltage frequency components from the
detected terminal voltage;
means for detecting an amperage of the currents, one input of said
amperage detecting means being connected to a terminal of the
storage battery and another input of said amperage detecting means
being connected to an output terminal of the alternator;
second means for extracting amperage frequency components at the
same frequencies as said voltage frequency components from the
detected amperage;
means for computing internal impedances of the storage battery at
each of said frequencies from the voltage and amperage frequency
components;
means for storing predetermined relationships between the internal
impedance, remaining capacity and remaining service life of the
storage battery for each of said frequencies; and
means for determining the remaining capacity and remaining service
life values of the storage battery at said frequencies from the
computed internal impedances and said predetermined
relationships.
3. A battery condition monitor as recited in claim 2, wherein said
voltage detecting means comprises a line connected to an input
terminal of an input/output interface of a microcomputer including
an analog/digital converter and connected to a terminal of the
storage battery and wherein an output terminal of said amperage
detecting means is connected to the input/output interface.
4. A method for monitoring the condition of a storage battery into
and out of which currents flow, said currents having components of
different frequencies, comprising the steps of:
detecting a terminal voltage of the storage battery;
detecting an amperage of the currents;
extractng frequency components the detected terminal voltage and
amperage signals at predetermined frequencies;
computing internal impedances of the storage battery at said
predetermined frequencies from the voltage and amperage frequency
components; and
determining the remaining capacity and remaining service life of
the storage battery at said predetermined frequencies derived from
the computed internal impedances, said determining step being
carried out in accordance with predetermined relationships between
the internal impedance, remaining capacity and remaining service
life of the storage battery for each of said frequencies.
5. A battery condition monitor as recited in claim 1, wherein said
predetermined relationships comprise functions formed by plotted
measured internal impedances of the storage battery for each value
of the remaining capacity of the storage battery at various levels
of the remaining service life of the storage battery.
6. A battery condition monitor as recited in claim 5, wherein said
determining means comprises a microprocessor means, said
microprocessor means operable for looking up in accordance with
said functions a point at which remaining capacities of the storage
battery at a first internal impedance of the storage battery,
computed at a first frequency, and at a second internal impedance
of the storage battery, computed at a second frequency, are in
agreement and at which remaining service lives of the storage
battery at the first and second internal impedances of the storage
battery are in agreement.
7. A method for monitoring the condition of a battery as recited in
claim 4, wherein said predetermined relationships comprise
functions formed by plotted measured internal impedances of the
storage battery for each value of the remaining capacity of the
storage battery at various levels of the remaining service life of
the storage battery.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a battery condition monitor and
monitoring method by which the remaining capacity and service life
of an storage battery, e.g. an automotive vehicle storage battery,
can be monitored.
2. Description of the Prior Art
The primary function of an automotive vehicle storage battery is to
supply current to a starter motor and an ignition system when an
engine is being started. It also supplies current for lights,
radio, and other electrical accessories when an alternator is not
handling the electrical demand. A battery condition monitor serves
to back the storage battery up and perform its essential function
when the remaining capacity and service life of the storage battery
drop below acceptable levels.
Japanese published unexamined patent application No. 53-127646
discloses a prior art battery condition monitor which measures the
remaining capacity of the storage battery by means of the supported
rate between the internal impedance and the remaining capacity of
the storage battery.
However, since this rate depends on the remaining service life of
the storage battery, the prior art battery condition monitor cannot
measure the remaining capacity of the storage battery
accurately.
SUMMARY OF THE INVENTION
An object of this invention is to provide a battery condition
monitor for a storage battery capable of accurately measuring both
remaining capacity and service life. In order to achieve this
object, this invention comprises means for computing the internal
impedances of the storage battery at various frequencies from the
voltage and amperage of battery output at each frequency, means for
storing a predetermined relationship between the internal
impedance, remaining capacity and remaining service life of the
storage battery for each of the frequency components and means for
looking up the remaining capacity and remaining service life of the
storage battery in accordance with the computed internal impedances
at each frequency. According to this invention, the exact remaining
capacity and remaining service life of the storage battery is
continuously monitored, so that maintenance of the storage battery
is facilitated.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram showing the principles of a battery
condition monitor according to this invention.
FIG. 2 is a block diagram of a battery condition monitor according
to a preferred embodiment of this invention.
FIG. 3 is a flowchart for the battery condition monitor of FIG.
2.
FIG. 4 is a graph of the relationship between the internal
impedance and the remaining capacity and service life of the
storage battery at frequency f1.
FIG. 5 is a graph similar to FIG. 4 but at frequency f2.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The preferred embodiments of this invention will be described with
reference to FIGS. 1 to 5.
As shown in FIG. 1, the battery condition monitor of this invention
comprises a voltage sensing element 1, an amperage sensing element
2, an impedance calculator 3, and a remaining capacity and
remaining service life calculator 4. "Remaining service life" of a
storage battery in question is used relative to full service life
of a new storage battery.
The voltage sensing element 1 continuously monitors the voltage
across the terminals of the storage battery in question. The
amperage sensing element 2 continuously monitors the current
flowing into and out of the storage battery. The impedance
calculator 3 calculates the internal impedances of the storage
battery at different frequency levels from the voltage and amperage
values sensed by the respective voltage sensing element 1 and
amperage sensing element 2. The remaining capacity and remaining
service life calculator 4 calculates the remaining capacity and
remaining service life of the storage battery from its internal
impedances at different frequencies and empirically determined
relationships between the internal impedances and the remaining
capacity and remaining service life of the storage battery.
As shown in FIG. 2, a storage battery 5 installed within an
automotive vehicle is connected in parallel to a generator or an
alternator 6 and a group of electrical loads 7 which includes a
starter motor, an ignition system and other electrical accessories,
e.g. lights, a radio and an air conditioner. The alternator 6 has a
rectifier (not shown) and supplies rectified current to both the
group of electrical loads 7 and the storage battery 5. Changes or
variations in this rectified current effect the current flowing
into and out of the storage battery 5. The operational modes of the
alternator 6 and each electrical load in the group 7 produce
different frequency components in the currents to and from the
storage battery 5.
The battery condition monitor according to an embodiment of this
invention comprises an amperage sensor 8, a microcomputer 9 and an
indicator 10, e.g. a liquid crystal display. The microcomputer 9
includes a microprocessor unit or MPU 11, a memory 12 which
includes ROM and RAM, and an input/output interface or I/O
interface 13 which includes a wave-forming circuit, an
analog/digital or A/D converter and a digital/analog or D/A
converter.
A signal representing the terminal voltage V(t) of the storage
battery 5 is sent to the I/O interface 13 via a line 14 working as
a voltage sensing element. The I/O interface 13 sends a
corresponding terminal voltage signal to the MPU 11 via its A/D
converter.
The input terminals of the amperage sensor 8 are connected to the
storage battery 5 and the alternator 6. The output terminal of the
amperage sensor 8 is connected to the I/O interface 13. The
amperage sensor 8 sends a signal representing the current amperage
I(t), e.g., 10 amps. to or from the storage battery 5 to the I/O
interface 13. The I/O interface 13 sends a corresponding current
amperage signal to the MPU 11 via its A/D converter.
The MPU 11 computes internal impedances, e.g. R.sub.f1 and R.sub.f2
of the storage battery 5 at different frequencies f1 and f2 from
the sensed terminal voltage V(t) and the sensed current amperage
I(t).
The memory 12 stores predetermined functions representing the
relationships between the internal impedance and the remaining
capacity and remaining service life of the storage battery 5 at
different frequencies f1 and f2. FIG. 4 shows three curves at the
0-, 50- and 100-percent remaining service life values corresponding
to the above functions at the frequency f1. FIG. 5 shows three
curves at the 0-, 50- and 100-percent remaining service life values
corresponding to the above functions at frequency f2.
It is apparent from FIGS. 4 and 5 that the internal impedance of
the storage battery 5 increases as the remaining capacity or
remaining service life of the storage battery 5 decreases.
The above curves in FIGS. 4 and 5 were obtained by plotting
measured internal impedances for each value of the remaining
capacity of the storage battery 5 at various levels of the
remaining service life of the storage battery 5. Conditions of the
above measurements are as follows:
(1) The kind of the storage battery is an automotive lead-acid
battery (12 V),
(2) The temperature is about 20.degree. C., and
(3) A method of measuring is one of JASO D101-77, JIS D5301-1973,
and SAE J539i and J240a.
The MPU 11 computes the remaining capacity and remaining service
life of the storage battery 5 from the internal impedances R.sub.f1
and R.sub.f2 and the functions shown in FIGS. 4 and 5. The
indicator 10 then displays the computed remaining capacity and
remaining service life of the storage battery 5.
The operation of the inventive battery condition monitor will be
described with reference to the flowchart of FIG. 3.
At a first step 15, the MPU 11 receives signals representing the
respective terminal voltage V(t) and the current amperage I(t),
e.g, 10 amps. into or out of the storage battery 5. At a subsequent
step 16, the MPU 11 extracts frequency components, i.e. voltages
V.sub.f1 and V.sub.f2 and amperages I.sub.f1 and I.sub.f2 at
frequencies f1 and f2, from the time-dependent terminal voltage
V(t) and current amperage I(t) signals. At a step 17 following the
step 16, the MPU 11 computes the internal impedances R.sub.f1 and
R.sub.f2 at the respective frequencies f1 and f2 according to the
following equations:
At a step 18 following the step 17, the MPU 11 looks up the
remaining capacity and remaining service life of the storage batter
5 from the functions shown in FIGS. 4 and 5.
The method of looking up the remaining capacity and remaining
service life of the storage battery 5 at the step 18 will be
described with reference to FIGS. 4 and 5. The MPU 11, using the
internal impedances R.sub.f1 and R.sub.f2 obtained at the frequency
levels f1 and f2, finds the point at which the remaining capacity
values of the storage battery 5 at the impedance R.sub.f1 and at
the impedance R.sub.f2 are in agreement and at which the remaining
service life of the storage battery 5 at the internal impedance
R.sub.f1 and at the internal impedance R.sub.f2 are in agreement.
In this cae, the MPU 11 searches for the point a at the level of
the internal impedance R.sub.f1 as shown in FIG. 4 and the point b
at the level of the internal impedance R.sub.f2 as shown in FIG. 5.
Both of the points a and b indicate that the remaining capacity of
the storage battery 5 is 60% and that 50% of its service life
remains.
At a step 19 following the step 18, the indicator 10 displays a 60%
value for the remaining capacity of the storage battery 5 and a 50%
remaining service life value.
In another embodiment, temperature compensation for the internal
impedance, which would provide more exact values for the remaining
capacity and remaining service life of the storage battery 5, could
be performed by detecting the temperature of the storage battery
5.
* * * * *